Mittwoch, 28. August 2013

Die Milchrevolution.

08/28/2013 13:56
NATURE reports on the findings of the LeCHE and BEAN anthropological research projects

"The Milk Revolution" is how the prestigious international
scientific journal Nature headlines an article on the EU project LeCHE,
which, after several years of highly successful research, has managed to
bring to light the spread of dairy farming in Europe and the
development of milk tolerance in adult humans. It was after the
transition from a hunter-gatherer society to that of a settled farming
culture in the Neolithic period that dairy-related animal husbandry
first evolved, and this practice spread from the Middle East to all of
Europe. The processing of milk to make cheese and yogurt contributed
significantly to the development of dairy farming, as this represented a
way of reducing the lactose content of fresh milk to tolerable levels,
making a valuable foodstuff available to the human population. Until
8,000 years ago, humans were only able to digest lactose, a form of
sugar present in fresh milk, during childhood because as adults they
lost the ability to produce endogenous lactase, the enzyme required to
break down lactose. Shortly before the first farmers settled in Europe, a
genetic mutation occurred in humans that resulted in the ability to
produce lactase throughout their lives. Increasing numbers of adults in
Central and Northern Europe have since been able to drink and digest
milk. "This two-step milk revolution may have been a prime factor in allowing
bands of farmers and herders from the south to sweep through Europe and
displace the hunter-gatherer cultures that had lived there for
millennia," specifies the article in Nature with reference to the LeCHE
project. Since 2009, this EU initial training network involving 12
postgraduate students and their mentors from different disciplines,
i.e., anthropology, archeology, chemistry, and genetics, has been
looking at the role played by milk, cheese, and yogurt in the early
colonization of Europe and has published numerous important articles on
the subject. Anthropologist Professor Joachim Burger of Johannes Gutenberg University
Mainz (JGU) was substantially involved in the establishment of the EU
project and its research activities. "To appreciate the significance of
our findings, it is important to realize that a major proportion of
present-day central and northern Europeans descend from just a small
group of Neolithic farmers who happened to be able to digest fresh milk,
even after weaning," explained Burger. His team investigated the
phenomenon of lactase persistence, i.e., the ability to break down milk
sugar, using skeletons from the Neolithic. "Among the most exciting
results obtained by the LeCHE group were the detection of milk fat
residues in numerous Neolithic pottery remains and the ability to model
the spread of positive selection of lactase persistence," said Burger.
Just 5,000 years ago, lactase persistence was almost non-existent among
populations in which its modern prevalence is greater than 60 percent.
The researchers assume that extensive positive selection and recurrent
waves of migration were responsible for this development, which – in
evolutionary terms – took place extremely rapidly. Burger has now initiated an additional EU project entitled BEAN
(Bridging the European and Anatolian Neolithic) to investigate the
origins of the first Europeans to settle in the Balkans and western
Anatolia. Adam Powell, a mathematician and population geneticist based
in London, will be contributing his skills as a modeler and statistician
to the team of Mainz anthropologists. To better understand the actual
world in which the early farmers lived, the BEAN researchers recently
visited archaeological sites in western Anatolia on a ten-day excursion.
"It became very clear to us there that the west of present-day Turkey
as well as the Balkans represent two key regions when it comes to the
history of the population of Europe over the past 10,000 years," stated
Burger.